Semiconductor device comprising windings constituting inductors

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority from prior French Patent Application No. 01-00818, filed Jan. 22, 2001, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to semiconductor devices and more particularly to integrated circuits, in which windings constituting inductors, in particular magnetically-coupled inductors, are made so as to constitute a transformer.

2. Description of Related Art

The production of a transformer comprising a spiral primary metal winding and a spiral secondary metal winding made in the same layer with the turns of the winding wound in parallel is known in the art. The production of a transformer with different outputs in two spiral secondary metal windings formed in the same layer with the inner ends of these two windings being connected by vertical vias, is also known in the art. Such a topography is known by the name “balun.” Such transformers are described in document 1998 IEEE, page 105.

Although the production of the transformer is useful, it is not without its shortcomings. One shortcoming is there is no way to supply two signals of equal amplitude. Another shortcoming is there is no way to supply two signals of equal magnitude but with a phase of 180°. Accordingly, there is a need to overcome these shortcomings and to provide a transformer that supplies two signals of equal magnitude but with a phase of 180°.

SUMMARY OF THE INVENTION

The present invention provides a semiconductor device with an integrated circuit formed over several levels and made in several layers. The integrated circuit includes a metal circuit capable of constituting two secondary inductors and a primary inductor, the geometry of which makes it possible, when it is magnetically coupled to this primary inductor, to supply two signals of equal amplitude but with a phase difference of 180°.

According to the invention, the device comprises a metal circuit comprising two parts wound into a spiral which have inner ends and outer ends between which they comprise branches which lie on either side of a median longitudinal region and the successive branches of which are connected by intermediate junctions crossing this median longitudinal region.

According to the invention, the parts wound into spirals are formed such that the branches of one of the parts and the corresponding branches of the other part, lying on either side of the median longitudinal region, are made in the same level and are symmetrical with respect to this median longitudinal region, that a common junction connects the inner ends of the parts and lies across the median longitudinal region, and that the intermediate junctions between the branches of one of the parts passes above or below the intermediate junctions between the branches of the other part.

According to the invention, the device comprises a common external connection means connected to the common junction and separate external connection means connected respectively to the outer ends.

Thus, the wound parts of the metal circuit constitute two secondary metal windings which are symmetrical and formed between the common connection means and the separate connection means, respectively, and constituting symmetrical inductors.

According to the invention, the primary winding comprises two parts wound into spirals which have inner ends and outer ends between which they comprise branches which lie on either side of a median longitudinal region and the successive branches of which are connected by intermediate junctions crossing this median longitudinal region.

According to the invention, the parts wound into a spiral are formed such that the branches of one of the parts and the corresponding branches of the other part, lying on either side of the median longitudinal region, are made in the same level and are symmetrical with respect to this median longitudinal region, that a common junction connects the inner ends of the parts and lies across the median longitudinal region, and that the intermediate junctions between the branches of one of the parts passes above or below the intermediate junctions between the branches of the other part.

According to the invention, the primary circuit comprises separate external connection means connected respectively to the outer ends.

According to the invention, the branches of the wound parts are U-shaped.

According to the invention, the outer ends of the wound parts are placed adjacently.

According to the invention, the intermediate junctions which cross are preferably such that one is in the level of the corresponding wound part and that the other consists of a bridge having a branch in another level and vias for connecting to the branches of the corresponding wound part.

According to the invention, the separate connection means are preferably symmetrical with respect to the median longitudinal region and the common connection means lies along this median longitudinal region.

According to the invention, the connection means preferably comprise branches which lie parallel to the median longitudinal region, the separate connection branches of the parts being made at the same level as these parts and the common connection branch being made at a level other than these parts and than the intermediate junctions and being connected to the common junction by vias.

According to the invention, the device preferably comprises an electrostatic screen which lies below the metal circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings.

FIG. 1 shows a circuit diagram of an electrical transformer comprising a primary circuit and a secondary circuit which are superimposed;

FIG. 2 shows a lateral schematic view of a semiconductor device including the transformer of FIG. 1;

FIG. 3 shows atop view of the primary circuit included in the semiconductor device of FIG. 2;

FIG. 4 shows a top view of the secondary circuit included in the semiconductor device of FIG. 2;

FIG. 5 shows a perspective view of a junction included in the aforementioned circuits; and

FIG. 6 shows a junction included in the aforementioned secondary circuit.

DETAILED DESCRIPTION OF AN EMBODIMENT

It should be understood that these embodiments are only examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others. In general, unless otherwise indicated, singular elements maybe in the plural and vice versa with no loss of generality.

In the drawing like numerals refer to like parts through several views.

With reference to FIG. 1, a transformer <b>1</b> which comprises a primary metal circuit <b>2</b> having a winding magnetically coupled to a secondary metal circuit <b>3</b> with two windings constructed in order to supply two signals of equal amplitude but with a phase difference of 180° between a common output and two other separate outputs, can be seen.

With reference to FIG. 2, a semiconductor device <b>4</b> in which the primary circuit and the secondary circuit are integrated in a superimposed manner in order to constitute the transformer <b>1</b>, these circuits being made by metal micro strips, can be seen.

This semiconductor device has five metallization layers formed at successive levels n, n+1, n+2, n+3, n+4. As will now be described, the primary circuit <b>2</b> is made in the layers n and n+1 and the secondary circuit <b>3</b> is made in the layers n+2, n+3 and n+4.

With reference in particular to FIGS. 2 and 3, it can be seen that the primary circuit <b>2</b> comprises two metal parts <b>5</b> and <b>6</b> wound into spirals which have inner ends <b>7</b> and <b>8</b> and outer ends <b>9</b> and <b>10</b>, each part <b>5</b> and <b>6</b> comprising one and a half turns produced and arranged as follows.

The wound part <b>5</b> has, from its inner end <b>7</b> and in the layer of level n+1, a U-shaped branch <b>11</b> which is located on a first side <b>12</b><i>a </i>of a median longitudinal region lying along a longitudinal axis <b>12</b>, a U-shaped branch <b>13</b> which lies on the second side <b>12</b><i>b </i>of the median longitudinal region <b>12</b> and a U-shaped branch <b>14</b> which lies on the first side <b>12</b><i>a </i>of the median longitudinal region <b>12</b>, the branches above being open on the side of the median region <b>12</b>.

As will be described more specifically below, the branches <b>11</b> and <b>13</b> of the wound part <b>5</b> are connected by an intermediate junction <b>15</b> which crosses the median longitudinal region <b>12</b> and which lies at 45° and the branches <b>13</b> and <b>14</b> are connected by a junction <b>16</b> which crosses the median longitudinal region <b>12</b> and which lies at 45°.

Similarly, the wound part <b>6</b> comprises, from its inner end <b>8</b> and in the layer of level n+1, a U-shaped branch <b>17</b> located on the second side of the median longitudinal region <b>12</b>, a U-shaped branch <b>18</b> located on the first side of the median longitudinal region <b>12</b> and a third U-shaped branch <b>19</b> located on the second side of the median longitudinal region <b>12</b>.

The branches <b>17</b> and <b>18</b> of the wound part <b>6</b> are connected by an intermediate junction <b>20</b> which lies across the median longitudinal region <b>12</b>, at 45° and the branches <b>18</b> and <b>19</b> are connected by an intermediate junction <b>21</b> which crosses the median longitudinal region <b>12</b>, at 45°.

The branches of the wound part <b>5</b> and the corresponding branches of the wound part <b>6</b> are arranged symmetrically with respect to the median longitudinal region <b>12</b>. Thus, the branches <b>11</b> and <b>17</b>, the branches <b>13</b> and <b>18</b> and the branches <b>14</b> and <b>19</b> lie symmetrical with respect to the median longitudinal region <b>12</b> and the intermediate junctions <b>15</b> and <b>20</b> cross at 90° and the intermediate junctions <b>16</b> and <b>21</b> cross at 90°.

The branch <b>13</b> of the wound part <b>5</b> lies between the branches <b>17</b> and <b>19</b> of the wound part <b>6</b> and the branch <b>18</b> of the wound part <b>6</b> lies between the branches <b>11</b> and <b>14</b> of the wound part <b>5</b>.

Like the aforementioned branches, the junction <b>15</b> of the wound part <b>5</b> and the junction <b>21</b> of the wound part <b>6</b> lie in the layer of level n+1.

As is shown most particularly in FIG. 5, the intermediate junction <b>16</b> crosses the intermediate junction <b>21</b> by forming a bridge which bypasses this intermediate junction <b>21</b>.

For this, the intermediate junction <b>16</b> comprises portions <b>16</b><i>a </i>and <b>16</b><i>b </i>which extend the branches <b>13</b> and <b>14</b> into the layer of level n+1 and which are interrupted at some distance from the intermediate junction <b>21</b>, an intermediate branch <b>22</b> made in the layer of level n and vertical vias <b>23</b> and <b>24</b> which join the ends of portions <b>16</b><i>a </i>and <b>16</b><i>b </i>and the ends of the intermediate branch <b>22</b>.

The intermediate junctions <b>15</b> and <b>20</b> are arranged so as to correspond to the intermediate junctions <b>16</b> and <b>21</b>. This time, it is junction <b>20</b> which is made in the form of a bridge.

The inner ends <b>7</b> and <b>8</b> of the wound parts <b>5</b> and <b>6</b> are extended and connected directly by an inner junction <b>25</b> which crosses the median longitudinal region <b>12</b>, perpendicularly, in the layer of level n+1.

The outer ends <b>9</b> and <b>10</b> of the wound parts <b>5</b> and <b>6</b> are arranged adjacently near the median longitudinal region <b>12</b> and are extended by separate external connection branches <b>26</b> and <b>27</b> which lie parallel to the median longitudinal region <b>12</b> and outward. These branches <b>26</b> and <b>27</b> are designed to be connected to a source of electrical energy from another component of the semiconductor device <b>4</b>.

Thus, the primary circuit <b>2</b> consists of a metal winding which is symmetrical with respect to the median longitudinal region <b>12</b>.

With reference in particular to FIGS. 2 and 4, it can be seen that the secondary metal circuit <b>3</b> also comprises two parts <b>28</b> and <b>29</b> wound into spirals which are constructed in the same way as the primary circuit <b>2</b>.

However, this time, the wound parts <b>28</b> and <b>29</b> comprise respectively three turns and are formed symmetrically with respect to a median longitudinal region identified by its longitudinal axis <b>30</b>.

The U-shaped branches of the wound parts <b>28</b> and <b>29</b> lie in the layer of level n+4 and the intermediate junctions which cross are made in the same way as the intermediate junctions which cross in the primary circuit <b>2</b>. Thus they have bridges <b>31</b> which have intermediate branches <b>32</b> which lie in the layer of level n+3.

The outer ends of the wound parts <b>28</b> and <b>29</b> are also extended by separate longitudinal connection branches <b>33</b> and <b>34</b>, which lie in the opposite direction to the connection branches <b>26</b> and <b>27</b> of the primary circuit <b>2</b>.

Furthermore, the secondary circuit <b>3</b> comprises a common longitudinal connection branch <b>35</b> which lies parallel to the median longitudinal region <b>30</b> and which is made in the layer of level n+2. This external connection branch <b>35</b> is connected to the inner junction <b>36</b> for linking the ends of the wound parts <b>28</b> and <b>29</b> by vertical vias <b>37</b>.

Thus, the secondary circuit <b>3</b> comprises wound parts <b>28</b> and <b>29</b> constituting two identical secondary windings formed respectively between, on the one hand, the common external connection branch <b>35</b> and the separate external connection branches <b>33</b> and <b>34</b>.

The vias <b>37</b> are located at the geometric center of the secondary windings, they correspond by construction to the electrical center of the metal circuit <b>3</b>.

The result of the structure described above is that the primary circuit <b>2</b> constitutes a primary inductor and that the secondary circuit <b>3</b> constitutes two secondary inductors, magnetically coupled to the primary circuit <b>2</b> constituting a primary inductor, such that the signals provided, on the one hand, between the external connection branches <b>33</b> and <b>35</b> and, on the other hand, between the external connection branches <b>34</b> and <b>35</b> are of equal amplitudes with a phase difference of 180°, these signals being delivered to other components of the semiconductor device <b>4</b>.

Since the primary circuit <b>2</b> and the secondary circuit <b>3</b> are made in different levels, this structure has the advantage of being able to define or choose, independently, the number of turns forming them so as to obtain the desired transformer ratio, this for a required orientation of the external connection branches, for example 180 degrees as shown in FIGS. 3 and 4, while having the advantage of leading to the production of a transformer of small size.

In addition, this structure makes it possible to control the geometric position of the outer ends so as to limit the length of the connections with other circuits of the required function and to facilitate the microwave characterization of the device.

Furthermore, this structure has the advantage of being able to be determined, before fabrication, using electromagnetic simulation tools so as to obtain the desired transformer ratio.

Moreover, in order to isolate the transformer <b>1</b> with respect to the substrate of the semiconductor device <b>4</b> and to benefit from stray capacitances with respect to the substrate when using methods of matching by external capacitors, it is desirable to have available, below the layer of level n, an electrostatic screen <b>38</b>.

It is important to note that the number of secondary windings can be increased from two to N, where the number of common junctions would also increase to N−1 and this is in the true scope and spirit of the present invention.

Although a specific embodiment of the invention has been disclosed, it will be understood by those having skill in the art that changes can be made to this specific embodiment without departing from the spirit and scope of the invention. The scope of the invention is not to be restricted, therefore, to the specific embodiment, and it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present invention.